If it's true, then they shouldn't listen to you. But then they can follow advice of anyone, including yours.
[1] https://en.wikipedia.org/wiki/Liar_paradox
"This sentence" = "This sentence is false."
[This sentence is false] is false.
"This sentence" = "This sentence is false is false."
[This sentence is false is false] is false.
"This sentence" = "This sentence is false is false is false."
[This sentence is false is false is false] is false.
...
If it's true, then they shouldn't listen to you. But then they can follow advice of anyone, including yours.
[1] https://en.wikipedia.org/wiki/Liar_paradox